1. Field of the Application
The invention relates generally to breastmilk pumps, and particularly to an improved breastpump assembly for expressing mothers' milk, which in one significant aspect, substantially eliminates any “dead volume” in pumping, especially in the area of the breast and nipple.
2. Description of the Related Art
Breastpumps are well known, and generally are comprised of breastshields (also referred to as hoods) that fit over the breast, a vacuum pump connected to the breastshield for generating an intermittent vacuum within the breastshield, and a receptacle for the milk that is pumped from the breast. Manually driven vacuum pumps are commonplace, as well as those that are driven by a motor (house current, battery, pneumatic, etc.).
The vacuum pumps of these devices intermittently generate a vacuum (or negative pressure) within the breastshield, with the breastshield covering the nipple and typically a substantial amount of the breast itself. The intermittent suction action of the pump serves to pull on the nipple, and so express milk, in an action that some have considered similar to suckling. The milk so extracted ordinarily flows from the breastshield into a collection container, e.g., a bottle, for storage and later use. A breastpump of the foregoing description is shown in U.S. Pat. Nos. 4,857,051, and 4,929,229, and reference thereto may be made for further detail on breastpumps in general. A recent advancement in these types of breastpumps is also disclosed in US Patent Publication 2008/0171970.
Breastshields typically have a funnel-shape, comprising a conical portion with a tubular extension, the latter sometimes referred to as the nipple tunnel. The nipple and surrounding breast are received in the conical portion, with the nipple often extending into the tubular extension. Under vacuum, the breast is pulled further into the breastshield, ordinarily with the nipple then being pulled into the tubular extension, with the surrounding breast thereby also typically being pulled further into the funnel.
A nursing mother's nipples may thus be forced against the wall of the nipple tunnel under vacuum. This may cause friction against the wall as the nipple moves deeper into the nipple tunnel. There can also be friction between the breast and the conical portion, as well as in the nipple tunnel. This is actually a back-and-forth movement under the intermittent vacuum, exacerbating the effects of the frictional engagement.
Researchers, particularly those working with Medela, have studied the manner in which infants breastfeed, and have come to seriously question the “conventional wisdom” on how a baby feeds from the breast. For instance, it appears that a vacuum instead of a stripping action is occurring during milk expression. Further, nipple placement is proximal to the hard/soft palate junction rather than at the junction. Ultrasound imaging shows that there is little to no air in the natural “system” when the infant is nursing. In other words, when the infant is latched onto the mother's breast, there is little to no air in the infant's mouth. The suckling action by the baby seems to radially compress as well as expand (or release some compression) the nipple; the nipple attempts to expand into the volume created as the baby's tongue moves away from the palate.
In contrast, in commercially available breastpumps used by mothers for expressing or extracting breastmilk for later use by the infant, air is present in the system, specifically in the breastshield into which the breast is placed. Once a mother's breast is in place, the pump must work not only to express the breastmilk from the breast but also must work to move the air in the system as well. This, understandably, affects the size of the pump, and the energy required to make the pump work.
Another observation of researchers is that, during nursing, the baby latches onto the mother's breast and the baby's tongue has continual contact and interacts with the nipple of the breast to bring about the flow of milk. In commercially available pumps, once the breast is inserted into the breast cup or shield, the vacuum generated by the pump typically pulls the breast further into the breastshield, ordinarily with the nipple then being pulled deeper into the tubular extension. The nipple tends to be more or less “free” within the nipple tunnel, except to the extent it may be pulled into contact with the nipple tunnel wall (or expands to fill the tunnel diameter because of the applied vacuum). When compared to nursing, the expression of milk with a breastpump of this conventional design can bring about some discomfort to the mother, and does not entirely duplicate the feel and conditions present in normal suckling.
Further, with the available breast pumps, a mother generally is in a substantially vertical position while pumping, and the bottle into which the breastmilk flows must be located in a position downwardly from the mother. This is because conventional breastpumps operate using gravity as the prime mover to move milk from the breastshield to the bottle. This limits the mother's activities while pumping; for example, she cannot recline to any great extent while pumping.